Importing/exporting DLL functions IS case-sensitive, and always has been. That behavior is tied to the OS DLL loader, which is case-sensitive. That is one of the only areas of the Delphi language that is case-sensitive. This is documented behavior, at least in part:
Writing Dynamically Loaded Libraries
A name specifier consists of the directive name followed by a string constant. If an entry has no name specifier, the routine is exported under its original declared name, with the same spelling and case. Use a name clause when you want to export a routine under a different name.
Procedures and Functions (Delphi)
In your importing declaration, be sure to match the exact spelling and case of the routine's name. Later, when you call the imported routine, the name is case-insensitive.